In modern telecommunication networks where transmission conditions on radio channels are changing rapidly while ever higher data rates are to be achieved it is among others important to be able to adjust the transmission power in order to accurately follow these changes and to ensure efficient use of the available transmission capacity. However, frequent changes of transmission power require frequent control signalling which may increase the signalling overhead and thereby interference. As a consequence, the capacity for data transmission may be decreased.
One way of tackling the problem of signalling overhead in modern wireless communication networks is the principle of gating. In short, gating means that control signals adjusting the power on the radio channel are sent only periodically. In this fashion, interference on the radio channel may be reduced and its capacity increased. Specifically on the uplink, i.e., between a mobile terminal (UE) and a base station, gating may increase the battery time of the UE and therefore the time available for data transmission and voice conversation.
For instance in the WCDMA/HSPA 3GPP R7 (Third Generation Partnership Project Release 7), gating of the UL DPCCH (Uplink Dedicated Physical Control Channel) is introduced and named UE DTX. Also control signals which are normally sent continuously on a separate control channel, may be sent when user data is sent on the E-DPDCH (Enhanced Dedicated Physical Downlink Channel) or HS-DPCCH (High Speed Dedicated Physical Control Channel).
As is known to the skilled person, different gating schemes yield different performance under different radio conditions and the performance is a trade off between less DPCCH overhead and good power control. Here, by performance it is meant how well the power control signalling follows the changing condition on the radio channel and how well the available transmission capacity on the radio channel is used.
Furthermore, choosing one particular scheme may lead to far from optimal performance if the channel is not as expected or if the channel changes during the session. Gating may increase transmission performance in scenarios where mobile terminals move at low speed in relation to the base station or base stations. At higher speeds, more intense DPCCH is necessary in order to improve the performance, since signal fading changes rapidly. It has been shown, however, that gating at very high speeds or difficult radio conditions will degrade the performance compared to not using gating.
A further difficulty when choosing gating scheme in an HSDPA scenario is that both cycle 1 and cycle 2 parameters need to be specified. In some cases, changing only one of the cycles may not change the performance, while changing both may not be optimal.
Some solutions suggested by known technology deal with the gating optimization problem by changing the length of the gating preamble, such as in U.S. provisional patent application 60/705,831. Others attempt using gating in combination with channel quality reports received from one or more UEs, such as in the US patent application 20070030828.
These and other disadvantages related to known technology are at least in part solved by the present invention.